A semiconductor device includes a first semiconductor layer, a second semiconductor layer, a first pad, and a second pad. A first opening and a second opening are formed in a first main surface of the first semiconductor layer. The second semiconductor layer is stacked on the first semiconductor layer. The first pad for wire bonding is disposed in the first opening. The second pad on which an alignment mark is formed is disposed in the second opening. A third opening and a fourth opening penetrate the second semiconductor layer. The first opening overlaps the third opening. The second opening overlaps the fourth opening.